Service 151 serves both residential estates and many schools between Hougang Central and Kent Ridge, passing through Hougang Avenue 3, MacPherson, PIE, Bukit Timah, Clementi Road and Kent Ridge Cres. The service provides bus connections to many institutions along the Bukit Timah and Clementi Road academic belt, as well as serving within the National University of Singapore (Kent Ridge Campus).

Demand for this service is very strong during the peak hours with student demand in addition to workers commuting between Hougang and the industrial estates near Tai Seng and MacPherson Road. During offpeak hours, demand is moderate to weak. As such, the route is operated by a large split-shift fleet on regular weekdays, with reduced numbers during school holidays.

An express version of this service, 151e, also operates during the weekday peak hours. It skips Dunearn Rd/Bukit Timah Rd (plying the PIE instead), and stops along MacPherson Rd in both directions.